1. Field of the Invention
This invention relates to a cord-lock for use in the head rail of a window shade or blind for securing the position of one or more cords that are used to adjust the shade or blind height.
2. Description of the Related Art
Window coverings, such as venetian blinds and concertina blinds, typically include means for raising and lowering them to any desired height, using cords. A cord can be pulled in one direction to raise the blind. To fix the position of the blind at the desired height, the cord is released, and a mechanical cord-lock prevents the cord from moving. In order to lower the blind, the cord-lock is released, and the cord is allowed to move upwardly, allowing the blind to lower under the effects of its own weight.
Mechanical cord-locks are known, such as rollers which hold cords between them. For example, U.S. Pat. No. 4,719,956 shows a mechanical cord-lock comprising: a fixed metal cylindrical roller which serves as a guiding surface, over which a cord moves; and a second movable metal roller which serves as a locking surface. The cord is threaded between the two rollers. The movable roller, upon moving upwardly, locks the cord between the two rollers.
Another cord-lock with a guide roller and a locking roller is shown in UK patent GB (2,271,600). This cord-lock comprises a second guide roller in the elongated part of the cord-lock body which is adapted to engage the cord in the head rail of the blind. The second rotatable guide roller is intended to reduce wear of the cord and those parts of the cord-lock which are in frictional engagement with the cord.